We report on new retrospective childhood health measures collected in the 2017 Transition into Adulthood Supplement to the Panel Study of Income Dynamics (PSID) and a matched comparison of these retrospective measures with prospectively collected indicators of childhood health obtained across multiple waves of the PSID Child Development Supplement. Our goal is to evaluate these measures against each other, and also to compare them with data from the National Health Interview Survey. We hypothesize that the prospective measures are likely to be more complete and accurate because they are collected contemporaneously or with a shorter recall period. Our findings suggest that the prospective child health measures consistently understate the prevalence of childhood health conditions due to parents’ apparent underreporting of previously reported conditions. Accounting for prior reported conditions leads to high comparability between prospective and retrospective reports, and also reveals a potentially unfixable problem with cross-sectional measures of child health.